Alpha-fetoprotein (AFP, α-fetoprotein; also sometimes called alpha-1-fetoprotein or alpha-fetoglobulin) is a protein that in humans is encoded by the AFP gene. AFP is a major plasma protein produced by the yolk sac and the liver during fetal development that is thought to be the fetal form of serum albumin. The AFP gene is located on the q arm of chromosome 4 (4q25). AFP binds to copper, nickel, fatty acids and bilirubin and is found in monomeric, dimeric and trimeric forms.